Germination of Tagetes minuta L. I. Temperature Effects

Initial studies have indicated that Tagetes minuta achenes have both a temperature and a light requirement for germination. Temperatures tested were 10, 20, 25, 30 and 35 °C. Germination was optimal at 25 °C under white light conditions. Under these conditions 100 per cent of achenes germinated within 7 days of imbibition. There was no germination at 10 or 35 °C either in the light or in the dark. Achenes imbibed and incubated at 35 °C for 4 days showed no visible signs of germination but on transfer to 25 °C, 100 per cent of these achenes germinated within 24 h. Furthermore, achenes given this high temperature (35 °C) treatment could be dried at 25 °C, re-imbibed at 25 °C and again 100 per cent of achenes germinated within 24 h of re-imbibition. This rapid germination response following removal from the high temperature regime could also be induced by transfer to temperatures of 20 °C or 20 °C (16 h) alternating with 10 °C (8 h).